ROS-responsive injectable hydrogels loaded with exosomes carrying miR-4500 reverse liver fibrosis

The reversal of liver fibrosis requires effective strategies to reduce oxidative stress and inhibition of hepatic stellate cell (HSC) activation. MiR-4500 regulates pathological angiogenesis and collagen mRNA stability, with the potential to inhibit fibrosis. Herein, we explored the inhibition of HSC activation in vitro by exosomes (Exos) carrying miR-4500 and encapsulated Exos^miR-4500 in an intelligent injectable hydrogel with biological activity and reactive oxygen species (ROS) responsiveness for application in oxidative stress environments. Briefly, reversible boronic ester bonds were integrated into gelatin-based hydrogels through dynamic crosslinking of quaternized chitosan (QCS) and 4-carboxyphenylboronic acid (CPBA)-modified gelatin. The QCS-CPBA-Gelatin (QCG) hydrogel scavenged excess ROS from the local microenvironment and released Exos^miR-4500 through the dissociation of boronic ester bonds, providing a favorable microenvironment and in situ sustained-release drug delivery system for Exos^miR-4500. The results showed that QCG@Exos^miR-4500 hydrogel has biocompatibility, biodegradability, and slow-release ability, which could effectively clear ROS and inhibit HSC activation and pathological angiogenesis in vitro and in vivo. Furthermore, transcriptome analysis suggests that the pharmacological mechanism of the QCG@Exos^miR-4500 hydrogel is mainly related to anti-oxidation, anti-angiogenesis, anti-fibrosis processes, and signaling pathways. Thus, our study demonstrates that an intelligently responsive Exos^miR-4500 delivery system based on injectable hydrogels is a promising strategy for the treatment of liver fibrosis.